This invention relates to a target projector such as might be used, for example, in automatically testing one's visual field. Measurement of one's visual field is important for a variety of reasons including the diagnosis of glaucoma as well as other human visual system diseases or impairments. In general, the prior techniques for determining one's visual field and any blind spots have been quite slow and tedious and require a definite subjective response from the person being tested in order to determine whether he has sighted the target at a particular location in his visual field. Additionally, the previously employed tests require administration by one having relatively high degree of skill such as an ophthalmic technician, optometrist or ophthalmologist. For example, in the most common type of visual field test, a hand-held target such as a small disc at the end of a wand, is moved about the subject's visual field by the examiner while the subject fixates on a central point. During movement of the hand-held target through the subject's field, the examiner asks the subject repeatedly whether he can see the movable target as it is passing from location to location. The examiner may plot, manually, the location of each point which is seen by the subject, or alternatively, he may plot those locations which the subject is unable to see, and which, therefore, define his blind spot.
In order to overcome the uncertainties and difficulties in the foregoing prior testing techniques improved techniques have been developed to automate the foregoing visual field test and to obtain an objective evaluation of the subject's visual field. By way of example, an improved method and apparatus is described in U.S. Pat. application Ser. No. 286,422, filed Sept. 15, 1972. The technique includes a means for projecting, automatically, and in sequence, a plurality of target images to the subject in selected, various locations within his visual field.